The present invention relates generally to auctioneering circuits that provide an output signal which is representative of the maximum of two or more electrical currents and, more particularly, to an auctioneering circuit that utilizes operational amplifiers to compare a plurality of voltage signals that are each representative of one of a plurality of alternating currents.
In certain types of electrical control apparatus, it is occasionally beneficial to provide an auctioneering circuit in which the output signal varies with and represents only the largest of a plurality of input currents. Various types of auctioneering circuits are known to those skilled in the art. Some auctioneering circuits first convert input currents to voltage signals which are then compared with other similarly provided voltage signals to provide an output signal which varies only with the maximum of the input currents and is representative of that highest current. Other types of auctioneering circuits provide a comparison of the input currents themselves and do not convert the input current signals to voltage signals prior to the comparison.
U.S. Pat. No. 3,689,801, which issued to Engel et al. on Sept. 5, 1972, describes a circuit breaker that comprises a current auctioneering circuit for obtaining a unidirectional output current that is substantially equal to the unidirectional output current of only one of a plurality of substantially constant, unidirectional current sources which each have a pair of output terminals. U.S. Pat. No. 3,590,326, which issued to Waston on June 29, 1971, discloses an overcurrent protective device of the time delay type which is responsive to the current in an alternating current circuit that is being protected. When an instantaneous current exceeds a predetermined value, the protective device produces an output following a predetermined time delay which may be of fixed duration or which may vary inversely with the magnitude of the current being sensed. U.S. Pat. No. 3,634,729, which issued to Hendry et al. on Jan. 11, 1972, discloses a circuit breaker having separable contacts and an operating means for opening and closing the contacts. This circuit breaker includes an overcurrent protective device that is responsive to the current in the separable contacts. U.S. Pat. No. 3,660,722, which issued to Wilson et al. on May 2, 1972, discloses a circuit breaker in which a current transformer is arranged to provide the energy or power necessary for the output of the device and also to provide a first signal which varies with the ground current in the system. Other means is provided to derive a second signal from the associated system which varies with the line current in the system for which the highest line current in the system with said protective device is arranged to respond to both of the signals. U.S. Pat. No. 3,611,037, which issued to Watson on Oct. 5, 1971, describes a protective relay device for detecting ground faults in a polyphase alternating current system. It produces an output when the ground current in the system being protected increases above a predetermined level. U.S. Pat. No. 3,634,730, which issued to Wilson on Jan. 11, 1972, discloses a circuit breaker comprising an overcurrent protective device which includes means that are responsive to the current in separable contacts and in an electrical circuit which is being protected. The circuit breaker is tripped when predetermined operating conditions occur.